"That thing is — ticking! Gotta try to defuse it before…"
from Swamp Thing #1 (Oct/Nov 1972) by Len Wein & Berni Wrightson
from Swamp Thing #23 (June/July 1976) by Gerry Conway & Nestor Redondo
from Saga of the Swamp Thing #1 (May 1982) by Marty Pasko & Tom Yeates
from Saga of the Swamp Thing #21 (Feb 1984) by Alan Moore, Steve Bissette & John Totleben
from Saga of the Swamp Thing #28 (Sept 1984) by Alan Moore & Shawn McManus
from Swamp Thing Annual #3 (1987) by Rick Veitch & Tom Yeates, et al.
from Swamp Thing #1 (May 2004) by Andy Diggle & Enrique Breccia
For contrast, here are the moments leading up to Alec Holland’s transformation into Swamp Thing from the 1991 cartoon:
[…] then there’s this, though there are lots of versions of that panel to choose […]